Fonts size are too small

[remi]

Hello,

I am running gnucash 1.8.9 with gnome 2 on a debain sarge (kernel 2.6.10).
The fonts size is too small (maybe size 6 or 5)in the toolbars and other 
GUI text.
Does someone has a clue to solve this problem ?
Here is the output of $gnucash :

remi at vaio:~$ gnucash
The font "-adobe-helvetica-medium-r-normal--*-120-*-*-*-*-*-*" does not 
support all the required character sets for the current locale "fr_FR at euro"
  (Missing character set "ISO8859-15")
  (Missing character set "ISO8859-15")
The font "-adobe-helvetica-medium-o-normal--*-120-*-*-*-*-*-*" does not 
support all the required character sets for the current locale "fr_FR at euro"
  (Missing character set "ISO8859-15")
  (Missing character set "ISO8859-15")

Gtk-WARNING **: invalid cast from (NULL) pointer to `GtkObject'
Gtk-CRITICAL **: file gtksignal.c: line 1067 
(gtk_signal_handler_block_by_data): assertion `object != NULL' failed.
[...]
Gtk-WARNING **: invalid cast from (NULL) pointer to `GtkCheckMenuItem'

The size for the operations in my accounts is just fine (a proper 12) 
like in all the informations I have to type in. It is jsut the "system" 
fonts size. All my others apps are ok.

I have installed 100dpi and 75dpi fonts.

Thanks a lots.
Rémi.